The present invention relates to a method and/or architecture for implementing oscillators generally and, more particularly, to a method and/or architecture for calibrating the operating frequency of a self contained, on-chip oscillator, using a single pin.
Conventional oscillators use external components (i.e., crystals, RC networks, resistors, etc.), to tune the operating frequency. Manufacturers typically factory trim the oscillator die and optionally fine tune the die with in-system measurements of known events in time to tune the oscillators. However, such tuning configurations are typically restricted to parameters such as die trim when the final package is pin limited and cannot include pins for fine tuning. Furthermore, in-system tuning can be relatively complex and can involve extra pins, special test modes, complex procedures, and specialized equipment.
It is generally desirable to provide simple on-chip tuning for oscillators using a limited number of pins and commonly available lab test equipment.
The present invention concerns an apparatus comprising an output circuit and a control circuit. The output circuit may be configured to generate an output signal oscillating at a frequency in response to a control signal. The control circuit may be configured to generate the control signal in response to (i) a frequency of said input signal when in a first mode and (ii) a stored value when in a second mode.
The objects, features and advantages of the present invention include providing a method and/or architecture for setting the operating frequency of a self contained, on-chip oscillator that may (i) be implemented using a single pin, (ii) allow accuracy to be determined by a signal source plus internal resolution, (iii) provide easy in-system features, (iv) be implemented without additional programming and/or (v) be implemented without special configuration modes such as a programming mode requiring special pins, modes, or programming voltages.